Novel Antimicrobial Host Defense Peptides: Design and Immunomodulatory Function

抗菌素耐药性（AMR）是一个日益重要的全球卫生问题，简单的细菌感染再次变得普遍和致命。最近的SARS-CoV2大流行进一步加剧了耐药性，因为即使只有一小部分患者出现细菌合并感染，对COVID-19患者的抗生素处方也严重过量。宿主防御肽（Host defense peptides, hdp）具有多种作用机制，如直接杀伤细菌和免疫调节特性，是抗耐药细菌的可行解决方案。尽管HDPs很有前景，但由于其快速降解、全身毒性和低生物利用度限制了其治疗效果，因此很少用于临床。在过去的6年里，斯特劳斯小组为提高hdp的适用性做了大量的工作。合成了对耐药菌具有高活性的新多肽，并对其作用机制进行了研究。此外，制定了减轻HDPs局限性的配方和缀合策略。由此产生的方法显示出巨大的希望。然而，为了进一步扩大HDPs的应用，需要进一步深入研究三个重要领域：1)了解免疫调节HDPs （iHDPs）在分子水平上的功能；2)通过了解缀合作用如何影响作用机制，为ihdp量身定制递送策略；3)开发重新利用常用抗生素的方法，以便为抗生素耐药性问题提供现成的解决方案。具体来说，本提案概述了目标，使不同的HQP团队能够发展成为独立的研究人员，具有跨学科，合作研究的强大培训和生物物理技术（例如NMR， ITC， CD等）的全面知识。学员将受益于一个以公平、多元化和包容为核心价值观的工作环境：斯特劳斯集团的大多数学员都是女性和少数族裔。为了了解iHDPs的作用机制（目的1），两位博士生将通过研究HDP/巨噬细胞相互作用（一个新的研究领域）来确定这些肽如何影响巨噬细胞分化。他们还将研究氨基酸组成如何调节免疫调节活性。在偶联方面(2)，两名博士生将进一步微调当前的方法，使其适应于ihdp，并确定（例如使用整个细菌细胞核磁共振）聚合物-HDP偶联物的作用模式与单独的HDP有何不同。最后，利用我们在偶联方面的知识，博士生将设计出由常用分子和HDPs组成的新抗生素的方法。通过这种方式，可以利用当前抗生素的优点（高活性、低毒），同时最大限度地减少耐药性的影响。总的来说，拟议的计划将确保获得解决AMR问题所需的新颖基础知识，以便开发切实可行的解决方案。

Antimicrobial resistance (AMR) is an increasingly important global health concern, with simple bacterial infections becoming once again prevalent and lethal. The recent SARS-CoV2 pandemic has further exacerbated resistance, because antibiotics are being heavily overprescribed to COVID-19 patients even when only small proportions display bacterial co-infection. Host defense peptides (HDPs) are a viable solution against resistant bacteria due to their diverse mechanisms of action, such as direct bacterial killing as well as immunomodulatory properties. Despite their promise, HDPs are however seldom used in a clinical setting because their therapeutic efficacy is limited by rapid degradation, systemic toxicity, and low bioavailability. In the last 6 years, the Straus group has done extensive work to improve the applicability of HDPs. New peptides, which are highly active against resistant bacteria, were generated and their mechanism of action was elucidated. Moreover, formulation and conjugation strategies that mitigate the limitations of HDPs were developed. The resulting approaches show tremendous promise. However, in order to further broaden the usage of HDPs, three important areas require further in-depth study: 1) understanding how immunomodulatory HDPs (iHDPs) function at a molecular level; 2) tailoring delivery strategies for iHDPs by understanding how conjugation impacts the mechanism of action; and 3) developing approaches to repurpose commonly used antibiotics in order to have ready solutions to the AMR problem. Specifically, this proposal outlines objectives that will enable a team of diverse HQP to develop as independent researchers, with strong training in interdisciplinary, collaborative research and thorough knowledge of biophysical techniques (e.g. NMR, ITC, CD, etc.). Trainees will benefit from a work environment where equity, diversity and inclusion are core values: most trainees in the Straus group are women and from visible minorities. To understand the mechanism of action of iHDPs (aim 1), two PhD students will determine how these peptides affect macrophage differentiation by studying HDP/macrophage interactions, a new area of research. They will also investigate how amino acid composition modulates immunomodulatory activity. In terms of conjugation (2), two PhD students will further fine-tune current approaches and adapt them to iHDPs, as well as determine (e.g. using whole bacterial cell NMR) how the mode of action of the polymer-HDP conjugate differs from the HDP alone. Finally, using our knowledge on conjugation, a PhD student will devise methods to create new antibiotics (3) consisting of commonly used molecules plus HDPs. In this way, the benefit of current antibiotics (high activity, low toxicity) can be harnessed, while minimizing resistance effects. Overall, the proposed program will ensure that novel fundamental knowledge required to address the AMR problem is obtained, so that tangible solutions can be developed.